The present invention relates to acid-stable aqueous solutions containing aromatic formaldehyde condensation products containing sulfonate and/or carboxylate groups and suitable additives, to the preparation thereof and to their use as leveling agents, dispersants or fastness improvers in textile finishing, as tanning agents for leather and in the stain resist finishing of textile materials.
Water-soluble aromatic formaldehyde condensation products are known per se (see “Ullmanns Enzyklopädie der technischen Chemie” volume 16 (1979), page 140) and can be prepared by methods as described for example in Houben-Weyl: “Methoden der organischen Chemie” G. Thieme Verlag Stuttgart (1963), 14(2), 263-292, DE-A-1 960 616, DE-A-1 961 369 and DE 39 05 083 A1.
The aromatic formaldehyde condensation products described in DE-A-1 960 616 and DE 39 05 083 A1 are highly effective agents for improving the wetfastnesses of textiles dyed with anionic and/or cationic dyes. They can further be used for reserving polyamides against direct dyes in the dyeing of polyamide-cellulosic blends. The disadvantage of these products is the fact that they are not stable in the acidic pH range in that they separate out precipitates in the acidic pH range. There are many applications, however, where acid stability of the products themselves and after dilution in water is desirable for wide and universal utility. When further ionic groups are introduced into the products in order to improve acid stability, the effectiveness of the condensation products deteriorates.
It is an object of the present invention to provide acid-stable aqueous solutions of aromatic formaldehyde condensation products.
This object is achieved, surprisingly, by combining aromatic formaldehyde condensation products with suitable auxiliaries to obtain acid-stable aqueous solutions which are also highly effective in a wide range of applications in the textile and leather sectors.